<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <div class="parent">
        <div class="test"></div>
    </div>
</body>
</html>
<style>
    /* 第一种 */
    /* .parent{
        border: 2px solid #333;
        width: 100px;
        height: 100px;
    }
    .test{
        width: 40px;
        height: 40px;
        background-color: pink;
        margin-top: 30px;
        margin-left: 30px;
    } */


    /* 第二种 */
    /* .parent{
        width:100px ;
        height: 100px;
        border: 2px solid #333;
        position: relative;
    }
    .test{
        width: 40px;
        height: 40px;
        background-color: pink;
        position: absolute;
        left: 30px;
        top: 30px;
    } */


    /* 第三种 */
    /* .parent{
        width: 100px;
        height: 100px;
        border: 2px solid #333;
        display: flex;
        justify-content: center;
        align-items: center;
    }
    .test{
        width: 40px;
        height: 40px;
        background-color: pink;
    } */
</style>